If you go to a local craft store you can find inexpensive lengths of very small nickel-plated chain, and lots of hobby stores will sell fine brass tubing (or you can order direct from K &S Metals). Get tubing that is just large enough for the chain to pass through it. Cut very short sections (maybe 3/16 inch) for top pieces and longer sections for the uprights. Solder or glue the top sections on perpendicular to the uprights and drill holes spaced along the uprights to match the spacing on the full scale railings. Then you can thread a length of chain through each hole on all your uprights and glue it on the first and last ones, and presto, chain railings. You can paint them or try something called Blacken-It to give them a dark matte finish.